This invention relates to a method for controlling a cupola which receives a portion of its heat energy from a plasma torch.
The cupola is a vertical cylindrical shaped furnace in which alternate layers of coke, metal scrap, and fluxing material such as lime stone are placed. The coke is burned and the heat thereby produced is combined with heat input of the plasma torch to melt the scrap to form iron.
U.S. Pat. No. 4,530,101 describes a plasma fired cupola in which plasma torches are utilized to melt metal turnings in nozzles connected to the lower portion of the cupola.
A related application entitled Plasma Fired Feed Nozzle filed May 8, 1985 and assigned Ser. No. 047-811 describes how a plasma torch and feed nozzle are attached to the cupola and may be utilized to feed particulate material to the lower portion of the cupola.
Another related application entitled A Plasma Fired Cupola filed May 8, 1987 and assigned Ser. No. 047809 describes the operation of a cupola in which turnings and fine metal chips make up approximately 75% of the metal charge.
An application entitled Replacement Of Coke In A Plasma Fired Cupola filed May 8, 1987 and assigned Ser. No. 047-808 describe the operation of a cupola in which coke is replaced with bituminous or authracite coal or utilizes pulverized coal to provide up to 25% of the carbon required to melt metal turnings and fine chips to form iron. In a cupola with a plasma torch and plasma torch feed nozzle, the melt rate chemistry and temperature of the iron produced are affected by the charge make-up, particulate feed through the feed nozzle, the blast air or recirculated gases and the output of the plasma torch which is effected by the field current, arc current and air supplied to the plasma torch.
The object of this invention is to provide a reliable control system which allows a very wide range of operating conditions for producing a wide range of iron chemistry utilizing fine borings and chips as a major portion of the scrap being melted.